Telephone trunking scheme



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Filed oci. 2, 1924 1a Sheets-Sheet l6 Patented 0.1. 18, 1921.

I 1,645,972 UNITED STATES PATENT OFFICE.

ERNEST JEAN CAMIL BOITSSEAU, OF LONDON, ENGLAND, ASSIGNOR 'rp THE DELAY AUTOMATIC TELEPHONE COMPANY, LIMITED, 01 LONDON, ENGLAND.

TELEPHONE TRUNK ING SCHEME.

Application filed October 2, 1924, Serial No. 741,165, and in Great Britain October 5, 1923.

The invention relates to the relative ar rangement of interconnecting lines in telephone systems, commonly known as trunking schemes.

According to my invention I provide a trunking scheme in which are a number of incoming lines, and a number of outgoing lines, of which any one of the former can be connected to any one of the latter over any one of a number of intermediate lines by means of intersecting member switches.

Several methods of distributing the various lines amongst the apparatus are conceiveable, but herein only two will be described.

According to one method the incoming lines are divided into a number of groups and each group is allocated to a primary intersecting member switch by means of which any one of the lines composing the group can have access to any one of a number of intermediate lines. The different intermediate lines from any one primary switch are connected to different secon ary intersecting member switches. one line from each primary going to each secondary switch. By means of the secondary switches any line incoming thereto can have access to any secondary intermediate line outgoing therefrom and as a consequence any line incoming to any of the primary switches can have access to any secondary intermediate line outgoing from any secondary switch. Similarly the various secondary intermediate lines from a secondary switch are in common with one line from each of the other secondary switches connected to different tertiary intersecting member switches. Thus, the lines incoming to any particular tertiai are from different secondary switc les. By means of the tertiary switches any secondary intermediate line incoming theretocan have access to any outgoing line. As a consequence of this distribution of lines any l ne incoming to any of the primary intersecting member switches can have access to any line outgoing from any tertiary intersecting member switch over any one of a plurality of intermediate lines.

If it be immaterial which outgoing line he used for a particular destination the tertiary switches (or some of them) may be omitted.

.coming lines are divided into, groups as beswitch i fore and each group is allocated to a primary intersecting member switch by means of which any one of the lines composing the group can have access to anyone of a number of intermediate lines. Each intermediate line from a primary switch in common with each such line from other primary intersecting member switches is connected to a different secondary intersecting member switch. Thus the lines incoming to any particular secondary switch'are from diflerent primary switches. By means of the secondary switches any line incoming thereto can have access to any secondary intermediate i line outgoing therefrom and as a consequence any line incoming to any of the pr mary switchescan have access to any secondary intermediate line outgoing from any secondary switch.

It will be observed that thus far the arrangement is the same for this method asfor the previously described method. All secondary intermediate lines outgoing from a particular secondary switch are connected to a tertiary intersecting member switch. In the tertiary switches each member in one direction has associated with it only one line whilst each member intersecting the first members would have associated with it as many lines as there are first members. The lines associated with the second member are multipled to similar second members in other tertiary switches.

The invention will be described by way of example in connection with the accompanying drawings, Figures 1, 2. 3 and 4. being referred to for the first method and Figures 5, 6. 7 and 8, for the alternate method.

Figure 1 shows a general layout of the I connecting apparatus and the manner of connectmg the various intermediate lines.

Figure 2 shows two groups of incomingthe secondary switches to the tertiary switches, Figure 4 shows one tertiary switch and -a group of outgoing lines.

Figure 5 shows a general'layout of the alternative trunking scheme, the trunking facilities being the same as shown in Figure 1 but the method of connecting the secondary to tertiary switches being slightly difierent.

Figure 6 shows two groups of incoming lines as shown in Figure 2.

Figure 7 shows two secondary switches, the line 5, 5 indicating the division between the two switches. The method ofconnecting from secondary switches to tertiary switches is in this case different.

Figure 8 shows two tertiary switches, line 5, 5 indicating the division between the two switches. This line 5, 5 also serves as an index line to show how Figures 7 and 8 1 Figures 2, 3, 4, 6, 7 and 8 are each placed on two sheets and lettered respectively a and b. In each of these figures the sheet lettered a should be placed to the left of the sheet lettered b, when reading the drawings.

Figures 9 and 10 show two ways of arranging the intersecting member switches. In Figures 1, 5, 9 and 10 the dotted lines represent the field of operation of one intersecting member, the connections being the same for each case. 1

By way of example I have shown a different type of switch in the method illustrated in Figures 5 to 8 from that illustrated in Figures 1 to 4. This is of course not necessary, either switch being suitable for either purpose. The switch for use with the arrangement shown in Figures 1 to 4 is of a well known type of intersecting member switch such, for instance, as those shown in British specifications Nos. 141005 and 141006. The switch shown in Figures 5 to 8 is composed of bar relays of the t pe described and claimed in'British speci cation No. 225932.

In Figures .6 to 8 only the controlling and-retaining circuits are indicated. The switches, of course, would carry conversation circuits similar to those shown in Figures 2 to 4. They have been left out in order not to crowd the drawing.

The means by which the requisite line or group of lines is determined and by which the connecting operations are initiated will not here be described as they form no part of the invention. It may be any type of selector but would preferably be a relay selector such as is described in British specification No. 181119.

Referring to Figure 1, it will be assumed that a connection is to be made from pricuit for itself at its contacts 13 to circuit 5.

mary group A to tertiary group TGl. A 11 calling line has become connected by any convenient means to line A, for instance, and can be connected to tertiary group TGl over any one of a number of routes, and these routes can, it will be easily seen from' 7 Figure 1, be taken through any one of the secondary switches: similarly by means of the arrangement of the trunking, line A can be connected to any line in any of the tertiary groups. The route chosen will de- 7 pend upon which route has all its component parts free. For the purpose of the description of the method shown in Figures 1 to 4 the following route will be assumed A A1 sei sG1 TG1*TT1.

The type of intersecting member switch used in Figures 2 to 4 is one in which the operation of a magnet selects a plurality of sets of contacts and the operation of another magnet operates particular sets of such con- 8 tacts. In switches of this type only ten selecting magnets and ten connecting magnets are required to connect any one of ten incoming lines to any one of ten outgoing lines. 9

Owing to previous I operations line A, Figure 2, is marked by the completion of circuit 2. In a similar manner TGl Figure 4, is marked by circuit 22 being prepared. It is not considered necessary to show or describe the means for completing these circuits beyond saying that it may be an impulse responding apparatus suitably designed. Circuit 22 would in general be prepared when the responding apparatus marked a wanted line and this line was testing for an idle line TT (Figure 4). In circuit 2 OTMl operates to complete circuits 3 and 4. Circuit 3 completes by its derivatives 5, 6, 7, 8, circuits for relays OLMl in SGl, OLM5 in SG2, other OLM relays in other SG groups.

OLMl operating completes a holding cir- It also prepares at its upper contacts extensions 14, 15, 16 and 17, of circuit 5.

Circuits 6, 7 and 8, by operating their respective OLM relays would cause the preparation of extensions similar to 14, 15, 16 and 17, prepared by OLMl. One of the exten- 810115 of circuit 6 prepared by the operation of OLM5 is shown as 18.

One extension (such as 14, 18) of each of the circuits 5, 6, 7 and '8, is brought to a i contact'of a relay ILB, Figure 4; each extension to a contact of a different ILB relay, and all the ILB relays appertaining to the same tertiary switch (TGl).

A second extension (suchas 15, 19) of the circuits 5, 6, 7 and 8, is taken to a contact of a relay ILB; each extension to acontact of a different ILB relay, and all the ILB relays appertaining to the same tertiary switch does not release before it has finishedits' similarly dealt with with reference to different tertiary-switches.

Circuit 22 is completed upon the operation of OLMl, OLM5, and so forth, byway of extension 14, 18, and the like. The completion of circuit 22 causes the operation of relay ITML Relay ITMl closes circuit 27 and also a holding circuit for itself. In circuit 27 relay SS operates and closes circuit 28 causing the operation of'ILMl; the completion of this circuit being extension 14-to relay OTMl. Circuit 28 is a chain testing circuit, that is, if secondary intermediate line SGrl is busy, ILBl would be operated and thus prevent circuit 28 from bein-gcompleted through relay ILMl. Circuit 28 would then be completed through relay ILM2 or an ILM relay of the first idle secondary intermediate line TGl. If SGl is free, however, the operation of ILMI cuts circuit 28 from the other ILM relays completes a circuit for itself independent of ILBl to ensure that it function, and also completes circuits 29 and 30. In circuit 29, relay LLCl operates. It

will be seen that circuit 30 is an extension. 1 of circuit 9 which itself is a derivative of circuit 4 prepared by OTMI. In it are in-' cluded OLCl and ILCl. Thus'ILGl and OLCl operate in this circuit. The previous operation of OTMl selected all those contact sets in the horizontal row with itself and the operation to this stage of 'OLCl operates that set which is in the vertical column with itself and is selected by OTMl. Similarly the previous operation of OLMl and of ITMl selected all these contact 'setsin the vertical column with itself and the operation at this stage of LLCl operates that set which is in the horizontal row with itself and is selected by OLMl whilst the operation at this stage of ILCl operates that set which is in the horizontal row with itself and is selected by ITMl.

Thus a holding circuit 31 shown by dotted lines is closed for relays ILCl, LLC1' and OLCl. -Relays ITB1, ILBl and OLBl are also included in circuit 31. The operation of ITB1 breaks operating circuit 22 of ITMl ,to prevent its subsequent operation. Relay ILBl operating breaks the operation circuit of ILM1 making secondary intermediate line SGrl test busy at subsequent connections.

The operation of OLB1 breaks the oper- OLMl is held over its own contacts until the marking operation is completed.

When the markin operation is completed the recorder, with rawsmarking current from relays OTMl and ITMl. These relays de-energize and break the holding circuit of OLMl and ILMl, the connections being held by relays ILC1,.LLC1, OLCl.

Relays ITB1, ILB1, OLB1, as explained above, cause the route to test busy.

When the connection is no longer required holding circuit 31 is broken and immediately all the apparatus are released and can be used for other connections.

' By slight modifications to the marking arrangement shown in Figure 4 the tertiary switch can be eliminated, the secondary intermediate lines then serving as trunks leadmg directly to a distant exchange. The method of effecting this is known in connection with a relay system and it is thereforethought unnecessary to describe the method here as it is so very similar to that known method. Broadly it involves the-elimination of all but one ITM relay and arranging for thisrelay to be marked directly from the recorder when a line to the distant exchange is wanted, and the elimination of the ILC relays and. the substitution of reslstances. For those who desire it a fuller description will be found in British specification No. 181120.

' The apparatus in connection with which the above trunking scheme has been described is of the general type disclosed in British specification No. 141005. It may be of any similar suitable construction of such type. i

This being so we have electeQo show and describe the trunking scheme shown in Figures 5, '9 and. 10, which is very similar to that shown in Figure 1, in connection with a switch consisting of bar relays of. the type shown in British specification No. 225932.

Figure 5 shows one method of arranging the bar relays. The primary groups have as arranged in a similar manner.

Figure 9 is a repetition of Figure 5 but the arrangement of the bar relays is such that the auxiliary coils in the primary and secondary groups prepare circuits which are completed by the operation of one bar relay common to the primary and secondary P Figure 10 isa further repetition of Figure 5 but arranged for a bar relay to serve con tacts in the secondary and tertiary groups.

It is not proposed to describe the methods shown in Figures 9 and 10 as it is thought that a brief description of Figure 5 will be suflicient for the understanding of the modifications shown therein. Figures 6. 7, and 8, show the circuit arrangements.

Referring to Figure 5 it will be assumed thata connection is to be made from a line in a primary group to a line in tertiary group TGl. The line in group A is assumed to be line A which it will be seen can be connected to any line in TGl over any of a number of routes landing through any one of the secondary switches; For the purpose of this description the following route will be assumed :A, A1, 8G1, 8G1, 'llGl, T'll of TGl.

Circuits 40 and 50 are marked in a similar manner to circuits 2 and 22 of the previous example. Relay OTMl Operates in circuit '40 and completes circuits 41 and 46. Circuit 41 .by its derivatives 42, 43, 44 and 45, completes the operating circuits for relays OLML QLMQ, OLMZS, OLM4, which hold over their own contacts in circuit 41. Circuit 46 by its derivatives 47, 48, 49 and 51,

prepares operating circuits for auxiliary coils AS, AS, AS, AS". The operation of OLMl extends circuits 41 as circuit 52 to circuit 50. Relays OLM2, OLE I3 OLM4, and so on. extend circuit 41 bv derivatives similar to 52, to circuit 50. Only one of these similar derivatives,namely, 54 extended by OLMQ, is numbered in the drawing. Relay ITMl operates in circuit 50. completes a holding circuit for itself, circuit 55 for SS1 and prepares circuits 56 and 57.

Relay SS1 operating in circut 55 completes circuit 56, which after joining wire 50 in Figure 7 is completed over wires 52, 54 in parallel, wire 41*, wire 41 to earth. Relay ILMI operating in circuit 56 completes circuits 57, 47 and 61, and prepares circuit 59. In circuit 57 the auxiliary coil TASl operates and marks the selected trunk; in circuit 47 (which was prepared by OTMl) auxiliary coils AS and LASl are operated, these coils marking the primary and secondary lines to be taken into'use;

' in circuit 61 relay PR operates and comfiletes circuit 59 which is an extension of 41. elays BB1, LBRl'and ILCl are energized in thiscircuit. When these relays operate the contacts selected by the energized coils AS, LASI and TASl are closed thus completing the circuit through from the lines- Incoming to the primary switch to the lines outgoing from thetertiary switch and completing circuit 60 which is a holding circuit for the relays themselves. The contacts 00, Figure 6. and SC, Fi ure 7, are opened by operation of the respective relays BR and LBR and prevent their respective routes being taken for later connections.

It will be clearly understood from the drawing that had any other tertiary trunk been marked such as the one associated with ITMQ. the route would have been completed over ILCQ and LBR2.

Had the route chosen been engaged circult 56,for relay ILMI would have been open at contacts SC so that this relay would have remained inoperative. An extension of circuit 56 for relay ILM2 would have existed. This'relay would thus have operated and have brought about a connection over the lowest secondary intermediate line in SG2 and primary intermediate line AQA.

In the arrangement shown in Figure 9 bar relay BB1 would, in addition to those operations which it performed in the arrangement shown in Figure 5, have performed those of LBRl, whilst in the arrangement shown in Figure 10 bar relay llLCl would in addition to the operations performed by it in the arrangement shown in Figure 5 have performed those of LBRL In all other es- I sential respects the arrangement of Figure 9 is identical with that of Figure 5.

What I claim is 1. In an automatic telephone system having a final connecting group adapted to be operated bymore than two digits, the combination of a group of trunks, a group of subscribers lines, an odd pluralit of sets of intermediate lines arranged in line ahead in the final connecting group, intersecting member switches adapted in a single selecting operation to connect a trunk to asubscribers line through lines to all the sets in series, and means for determining the subscribers lines which are to be connected through the intermediate lines to the group of trunks before the intermediate lines through which such connection is to be made are selected.

2. In an automatic telephone system having a final connecting group adapted to be operated by more than two digits, the com bination of a group of trunks, a group of subscribers lines, a plurality of pairs of sets of intermediate lines arranged in line ahead in the final connecting group, intersecting member switches adapted in a single selecting operation to connect a trunk to a subscribers line through lines to all the sets in series, an means for determining the subscribers 'lines which are to be connected through the intermediate lines to the group of trunks before the intermediate lines through which such connection is to be made are selected.

3. A telephone system as claimed in claim 2 in which the lines of the first order are divided into groups, the intermediate lines of thefirst order are divided into groups, one line from each group of intermediate lines of the first order being assigned to each group of lines of the first order, the lines of the second order are divided into groups, the intermediate lines of the second orderv are divided into groups,

.one line from each group of intermediate 

